An abacus was used for counting and adding up before calculators. It is made from beads on a frame that you slide backwards and forwards.
An air conditioner is a device that changes the temperature of air that goes through it. Most airconditioners are for cooling air down. They work either by evaporating water inside them to make the air cool the same way that sweating cools you off, or they work by transferring heat from inside to outside by a heat pump. Some airconditioners are called reverse cycle because they can be used to heat your house too.
An alarm is a device or a signal that warns people of something happening that they need to pay attention to, such as a fire, a burglary or just that they need to wake up!
An amplifier is a device that increases the amplitude of a signal. For most people, this means it takes sound and makes it louder. Modern amplifiers also take incoming electrical signals and turn them into sound. When you plug headphones into your iPod, the amplifier in the headphones converts the signal from the iPod into sounds.
An ATM is an Automatic Teller Machine. You put your keycard or credit card into it to deposit or withdraw money.
An axle is a shaft that goes through the center of a wheel, which the wheel rotates around. One axle may have only one wheel or many wheels on it. Axles generally only have two wheels on them, one at each end.
A barbecue, barbeque, BBQ, Bar-B-Q or Bar-B-Que is a way of cooking food using heat and smoke from a fire. Barbeques are usually used to cook meat.
A battery is a device that stores electricity. Things that have batteries still need power to run, but you don't have to plug them in to a power point in your house. When a battery runs out of power, you need to get a new battery or recharge your old one.
Binoculars, also called field glasses, are a special kind of glasses that function like two small telescopes, one for each eye. They let you see things in the distance as if they are much closer. Binoculars are smaller and easier to use than a telescope, and are more pleasant to use as you do not need to close one eye to look through binoculars.